Microplastic abundance, distribution and composition in the Pearl River along
Guangzhou city and Pearl River estuary, China
Muting Yan a, b, 1, Huayue Nie a, b, 1, Kaihang Xu a, b, Yuhui He a, b, Yingtong Hu a, Yumei Huang a, b, **, Jun Wang a, b, * a
College of Marine Sciences, South China Agricultural University, Guangzhou 510642, China b Joint Laboratory of Guangdong Province and Hong Kong Region on Marine
Bioresource Conservation and Exploitation, South China Agricultural University,
Guangzhou 510642, China h i g h l i g h t s
g r a p h i c a l a b s t r a c t First comparison of
microplastics between estuary and urban section of the Pearl River.
Films were the main shape in the Pearl River.
PA and cellophane were the dominant polymer types in the Pearl River.
Waste water effluents from urban city might
be a main source of microplastics. a r t i c l e i n f o a b s t r a c t Article history:
Like many urban rivers, the Pearl River in China is contaminated with microplastics. Compared with marine environments, Received 25 September 2018
microplastic pollution in freshwater is less understood, especially in urban rivers. In the present study, the abundance and Received in revised form
distribution of microplastics in water from the Pearl River was investigated, including the estuary and the urban section along 8 November 2018
Guangzhou. The average abundance of microplastics was 19,860 items/m3 and 8902 items/m3 in the urban section and estuary, Accepted 13 November 2018
respectively. Wastewater effluents from cities might be a main source of microplastics in the Pearl River, and the urban
Available online 14 November 2018 Handling
tributaries might act as retention systems for microplastics. Among these microplastics, over 80% of them were less than 0.5 Editor: Tamara S. Galloway
mm. The main shapes of microplastics were film, fragment, and fiber, mostly blue or transparent. Moreover, the most
common polymer types of these microplastics were polyamide (26.2%) and cellophane (23.1%). This study reveals the
contamination and characteristics of microplastics in the Pearl River, and provides important data for further research on
microplastics in freshwater ecosystems. Keywords:
© 2018 Elsevier Ltd. All rights reserved. Microplastics Water Pearl River estuary Urban section Human activity 880
M. Yan et al. / Chemosphere 217 (2019) 879e886 1. Introduction
* Corresponding author. College of Marine Sciences, South China Agricultural University,
2017). Several studies have reported that microplastics pollution was observed in Guangzhou 510642, China.
the Pearl River, Hong Kong and Guangdong coastal areas, and the PRE (Fok and
** Corresponding author. College of Marine Sciences, South China Agricultural University,
Cheung, 2015; Li et al., 2018a; Lin et al., 2018). However, the difference and Guangzhou 510642, China.
relationship between microplastics pollution in the PRE and the Pearl River,
E-mail addresses: huangyumei@scau.edu.cn (Y. Huang), wangjun2016@scau. edu.cn (J. Wang).
especially in urban sections, is still unknown.
1 These authors contributed equally to this work.
In this study, we focus on microplastic contamination in the estuary of the
Plastics are organic synthetic polymers, which have been used widely around
Pearl River and its urban section along Guangzhou, in particular, to figure
the world mainly due to their affordability, bioinertia, and high strength-to-weight
out whether urban tributaries act as retention systems with higher microplastic
ratio. It was estimated that over 250,000 tons of discarded plastics were deposited
densities than estuaries. The abundance, size, color, and shape of
from land into the ocean in 2014 (Eriksen et al., 2014). After weathering and
microplastics in surface water from 26 sites were investigated. We also
ultraviolet radiation, larger plastic debris degrade into smaller pieces, and those
explored the polymer types of microplastics by Raman spectra. This study will
measuring less than 5 mm are named microplastics (Thompson et al., 2004).
https://doi.org/10.1016/j.chemosphere.2018.11.093 0045-6535/© 2018
Elsevier Ltd. All rights reserved.
Apart from this source, microbeads from daily beauty and health products such
provide basic data for monitoring microplastics in the water resources of
as toothpastes and cleansers also contribute to microplastics pollution. Most of southern China.
these tiny microbeads are made of polyethylene, which can easily flow past
water filtration systems and enter lakes and oceans (Auta et al., 2017). Tiny 2. Materials and methods
fibers produced during washing are also microplastics. Due to the various
sources, microplastics in the environment occur in different shapes, such as 2.1. Sampling
fragments, spheres, and fibers. As a potential threat to humans, microplastics
pollution has become a growing concern in the world.
Water samples were collected from 26 sites in the Pearl River in December
Microplastics in the marine environment are easily introduced into the food
2017, as shown in Supplementary Table S1. Before sampling, all tools were
chain of the ocean because of their more available small size for ingestion. A wide
cleaned using distilled water. Samples of 20 L of surface water were collected
range of marine organisms have been reported to take up microplastics, such as
using a 5 L water sampler and then passed through a 50 mm stainless steel
zooplankton, bivalves, shrimp, fish, and whales (Cole et al., 2013; Lusher et al.,
sieve. The residue on the sieve was washed with pure water and removed into
2015a; Ferreira et al., 2016). The intake of these tiny particles can cause great
50 mL glass bottle (Lin et al., 2018). Two water samples were taken in the
harm to organisms, including reduced growth rate, pathological stress, oxidative
same way at each location. Before the experimental analysis, samples were
stress, and reproductive complications. Moreover, toxic chemicals attached to the preserved at 4 C.
particles also pose a great risk to marine organisms because of the bigger
specific surface area and stronger adsorption ability of microplastics (Reisser et
2.2. Microplastic extraction
al., 2014). Previous studies have reported that microplastics often accumulate in
the tissues of animals, and are difficult to remove and ingest (Auta et al., 2017).
In the laboratory, to dissolve the natural organics in the water sample,
Acting as vehicles to transport pathogens and toxic pollutants, accumulated
samples were treated with 30% H
microplastics in animals can eventually be transferred to humans through the
2O2 for 24 h at room temperature in the dark
food chain, causing serious health problems (Wang et al., 2016).
(Nuelle et al., 2014). Then the samples were filtered through 0.45 mm filter
Microplastics have been detected in growing numbers in waters and
paper under a vacuum pump, and the filter papers were placed in a dish and
sediments throughout the world, at especially high levels in lakes and rivers. In
air-dried at room temperature.
recent years, these small plastics have even been observed in deep-sea sediments
and Arctic polar water (Lusher et al., 2015b; Van Cauwenberghe et al., 2015).
2.3. Microscope inspection
Studies also demonstrate that microplastics are widely detected in waters in Spain
(Iniguez et al., 2017), England (Martin et al., 2017), Australia (Reisser et al.,
The particles were observed on the filter paper with a stereomicroscope
2013), and the USA (Gray et al., 2018). Microplastics found in waters are mainly
(Optec SZ680) and measured with an eyepiece micrometer. Based on previous
composed of polypropylene (PP), polyethylene (PE), polystyrene (PS),
studies (Cole et al., 2011; Hidalgo-Ruz et al., 2012), microplastics can be
polyethylene terephthalate (PET) and polyvinyl chloride (PVC). Microplastics
divided into three types according to their morphology: fiber, fragment, or
composed of different materials have different environmental behaviors. Those
film. They were also divided into five categories according to color: green,
mainly composed of PET and PVC are more likely to sink, while PP, PE, and PS
blue, transparent, red, and other. According to the size, microplastics are
more easily float. Polyamide (PA) and polyvinyl alcohol are common
divided into six classes: class 1, <0.5 mm; class 2, 0.5e1 mm; class 3, 1e2
components of microplastics as well (Carr et al., 2016). As these materials are
mm; class 4, 2e3 mm; class 5, 3e4 mm; and class 6, 4e5 mm. The quantity,
difficult to degrade by microorganisms, microplastics often persist in our
type, color, and size of the microplastics in each sample were recorded.
environment in all forms, including table salt, beer, sugar, dust in our homes, and
even bottled water samples (Kosuth et al., 2018). The concern about the impact
2.4. Microplastics identification
of microplastics is increasing, along with a significant increase in the amount
of microplastics in the environment.
Microplastics cannot be completely accurately identified by visual
China is the largest plastics producer in the world (Jambeck et al., 2015).
observation alone (Silva et al., 2018). Raman spectroscopy can be used to
Guangzhou, one of the most important megacities in China, is a representative
analyze the composition of sample particles, as previously reported (Araujo
city with massive plastic production and waste due to the huge population and
et al., 2018). In this study, 130 samples were randomly selected and analyzed
intensive anthropogenic activities. In 2016, nearly 10 million tons of plastics
by micro-Raman spectroscopy (Thermo Fisher Scientific DXR2, 532 nm
were produced in Guangdong (Li et al., 2018a). The extensive use and discarding
of plastics in Guangzhou greatly increase the microplastics burden in the Pearl
laser, Raman shift 503500 cm1). The obtained spectra were compared with the
River (Lin et al., 2018). Eventually, microplastics will enter the South China Sea
spectral libraries on the instrument. In addition, several particles were selected
through the Pearl River Estuary (PRE). As transitional zones between rivers and
for analysis by scanning electron microscope (SEM; Hitachi S-4800, Japan).
oceans, estuaries play a vital role in microplastics transportation. To date, coastal
Particles were placed on double-sided tape and coated with evaporated gold
areas along the PRE have become hotspots of microplastics pollution (Fok et al.,
before SEM observation. The number of microplastics for each sample was
M. Yan et al. / Chemosphere 217 (2019) 879e886 881
recalculated after removing the non-microplastics, as previously reported (Di
3.2. Microplastic characteristics and Wang, 2018).
The size of microplastics surface water from GUS was similar to that from
PRE, ranging from 0.05 mm to 5 mm. Over 80% of the microplastics were less
2.5. Quality assurance and control
than 0.5 mm in all detected samples, while only a small amount of 4e5 mm was
observed (Fig. 2A). A higher proportion of microplastics of 0.5e2 mm was found
To prevent external pollution from affecting the research results, the
in waters from PRE, though the difference was not significant due to the limited
experimenter needs to wear a cotton test suit and cannot wear plastic gloves.
samples. The amount of microplastics decreased as the length increased.
The sampler and stainless steel sieve used for sampling need to be rinsed with
Microplastics of 2e3 mm were significantly reduced in waters from PRE than
pure water in advance. Sampler and sieve need to be washed with pure water
from GUS (p < 0.05), and microplastics of 4e5 mm were not detected in waters
after sampling at each location. The water-filled glass container needs to be
from PRE (Fig. 2B). The color of microplastics was also recorded. In this study,
rinsed 3 times with pure water and baked at 120 C for 4 h.
blue and transparent items were prevalent in all water samples, constituting 38%
and 37% of microplastics, respectively. Smaller proportions of green and red
plastic items were also found in these samples (Fig. 3).
2.6. Statistical analysis
Typical microplastics are shown in the photographs in Fig. 4AeD.
Numerical data are presented as the mean
Microplastics in these samples were classified into three shapes: film, granule, ± standard error (SE). Data
analysis was performed by SPSS. The means of 2 groups were compared by
or fiber. Briefly, film is a thin piece of plastic debris, granule is a spherical
independent-samples t-test. The differences were regarded as significant at
or cylindrical piece or fragment, and fiber is a thin and long item. When an item
*p < 0.05 and extremely significant at **p < 0.01 in all cases.
could not be defined as fiber or film, it was classified as granule. Different
proportions of the three shapes were observed at different sampling sites (Fig.
4E). Film was the most dominant component, with a proportion of 52% in 3. Results
samples from GUS, followed by granule and fiber, constituting 41% and 7%,
respectively. In waters from PRE, the abundant components were granule and
3.1. Abundance and distribution
film, with proportions of 48% and 43%, respectively. Similarly, the amount of
fiber was the least, accounting for only 9% of microplastics. No significant
Microplastics were widely detected in all water samples collected from 31
difference was observed in the shapes of microplastics from these two areas (Fig.
sites in the Pearl River, with significant spatial variations in their
4F). Typical plastic-like particles were further analyzed by SEM. Generally, the
distribution. The abundance of microplastics in the Guangzhou urban section
surface of polymers was unregulated or smooth (Fig. 5AeF). Moreover, a large
(GUS) of the river and PRE varied from 8725 to 53,250 and 7850 to 10,950
amount of transparent pellets (Fig. 4C and D, red arrow) observed in this study
items/m3 of water, respectively (Fig. 1). A high density of microplastics of
were determined as diatoms according to the regular holes on their surface (Fig.
over 20,000 items/m3 was detected in S1, S2, S3, S6, S8, S9, and S11, all of 5G and H).
which were located near industrial parks or logistics parks. The lowest
abundance (<8000 items/m3) was found in P5 and P7, which were at the PRE
3.3. Composition of the microplastics
and far from the city center. The microplastics levels showed less variance in
samples from PRE (Fig. 1B). In addition, the average microplastics abundance
To identify the composition of the microplastics, a total of 130 items were
in GUS (mean 19,860 items/m3) was over two times higher than that in PRE
randomly selected and observed by micro-Raman
(mean 8902 items/m3) (p < 0.01). Therefore, microplastics pollution in the
urban section of the Pearl River was more serious than in PRE.
Fig.1. The abundance of microplastics in the Pearl River. Red column represents the abundance of microplastics in the surface water. Inset A shows the positions of sampling sites in Guangdong, China.
Inset B shows a comparison of microplastic abundance between the estuary and the urban section along Guangzhou (**p < 0.01). (For interpretation of the references to color in this figure legend, the
reader is referred to the Web version of this article.) 882
M. Yan et al. / Chemosphere 217 (2019) 879e886
Fig. 2. Sizes of microplastics in the Pearl River. (A) Percentages of different-size microplastics at 26 sampling sites. (B) Comparison of different-size microplastics between the
estuary and the urban section along Guangzhou (*p < 0.05).
spectroscopy. The results showed that 112 of them were microplastics. For all
samples, polyamide was the most common polymer type (26.2%), followed by
cellophane (23.1%), polypropylene (13.1%), and polyethylene (10.0%). A few
items were identified as vinyl acetate copolymers (VACs) and
polyvinylchloride (Fig. 6A). The Raman spectra of typical microplastics are
shown in Fig. 6B. The other 18 items were determined as non-microplastics as
their spectra were matched below 70% when compared with the spectra database. 4. Discussion
In the present study, the abundance of microplastics in samples from GUS
was significantly higher than from PRE, indicating that wastewater effluents
from urban cities might be a main source of microplastics in the Pearl River and
the urban tributaries might act as retention systems for microplastics. Seven of
the 26 sampling sites near industrial parks or logistics parks showed a value of
over 20,000 items/m3 in our study, which was not surprising, because
microplastic inputs are expected to be much higher in industrialized watersheds
Fig. 3. Colors of microplastics in the Pearl River. (For interpretation of the references to color in
this figure legend, the reader is referred to the Web version of this article.)
(Anderson et al., 2016). Besides, insulated boxes are widely used in logistics
parks for transporting, which can easily enter water drainage systems when they are improperly disposed,
Fig. 4. Types of microplastics in the Pearl River: (A) film, (B,C) granule, (D) fiber. (E) Distribution of microplastics at 26 sampling sites by type. (F) Comparison of different types of microplastics
between the estuary and the urban section along Guangzhou; no significance was observed. Red arrows indicate diatoms. (For interpretation of the references to color in this figure legend, the reader
is referred to the Web version of this article.)
M. Yan et al. / Chemosphere 217 (2019) 879e886 883
Fig. 5. SEM images of microplastics in the Pearl River: (A,B) fiber, (C,D) film, (E,F) granule, (G,H) diatoms.
thus contributing to the microplastics pollution nearby (Fok and Cheung,
2016; Rodrigues et al., 2018). A previous study reported that microplastics
2015). Although S10 is next to Xiyu Industrial Park, it is also located near the
were widely distributed in the Pearl River along Guangzhou, ranging from
famous Guangzhou Haizhu National Wetland Park. Lower population density
379 to 7924 items/m3 in waters sampled in July 2017, which were much lower
and human activities resulted in a lower concentration of microplastics.
levels than those in our study (Lin et al., 2018). As reported previously, the
As the monitoring method is still not unified, it was difficult to compare
distribution of microplastics in water can be affected by various factors, such
our results with other studies. However, we can compare the microplastic
as weather, the ambient environment, and nearby human activities (Thiel et
abundance with that reported in other research using similar methods and
al., 2003; Browne et al., 2011; Kukulka et al., 2012). Seasonally, the
expressive units. In comparison with worldwide microplastic pollution
microplastic abundance in water would be expected to be lower in July, since
(Supplementary Table S2), the abundance of microplastics in the Pearl River
the rain events in summer are more intense than in winter in Guangdong
was much lower than that of the Saigon River in Vietnam (Lahens et al., 2018).
Province. Microplastics were also detected in oysters along the PRE, which
Levels of microplastics in GUS were almost two times those of Taihu Lake
ranged from 1.4 to 7.0 items per individual and were positively related to those
and Hong Kong beaches in China (Fok and Cheung, 2015; Su et al., 2016),
in surrounding water (Li et al., 2018a). These results
similar to that in the Seine River of France (Dris et al., 2015). The microplastic
abundance in PRE was similar to that in the Three Gorges Reservoir (Di and
Wang, 2018), but still much higher than the levels monitored in the Antua
River of Portugal and the Great~ Lakes tributaries of the USA (Baldwin et al., 884
M. Yan et al. / Chemosphere 217 (2019) 879e886
Fig. 6. Composition of selected items identified by micro-Raman spectroscopy. (A) Percentage of plastic types in the selected items; (B) Raman spectra of typical microplastics.
indicate that microplastic may transfer in the food chain and pose potential threats
al., 2014; Sadri and Thompson, 2014). However, these results were quite different
to aquatic organisms and human.
from some previous studies, in which fiber was the most dominant shape
The high proportion of microplastics smaller than 500
(Lusher et al., 2014; Lin et al., 2018). This indicates that microplastic mm was not surprising,
characteristics may be related to the sampling area and the source of plastic in the
and correlated with some previous reports. Similarly, the most common size of
water. Granules are widely used as material for cosmetic scrubbers or plastic
microplastics observed in the Yellow Sea and Bohai Sea was in the range of
production. Cosmetic products such as facial cleanser and toothpaste contain
50e500 mm (Zhao et al., 2018). In Taihu Lake, sizes ranging from 100 to 1000
numerous plastic granules (Napper et al., 2015). Due to the high density of human
activities along the Pearl River, these microplastics in the shape of film or
mm were more frequent in the observation of microplastics (Su et al., 2016).
granule are likely delivered from urban wastewater or caused by degradation and
fragmentation of plastic debris, such as bottles, bags, and wrappers (Free et al.,
Small microplastics (<250 mm) were predominant and large size classes (>1000
2014). Currently, the specific mechanism of how plastic degrades and fragments
mm) were barely represented in the Saigon River (Lahens et al., 2018). The
is still unknown, and the effect on determining microplastic density in water needs further investigation.
enrichment of smaller-size microplastics may be because microplastics from
wastewater treatment plants are mainly less than 0.5 mm in size (Mason et al.,
Determining the origins of microplastics in water is not easy, but their
2016). Another explanation may be that large pieces of plastic could gradually be
polymer types may provide a potential indication. In this study, PA,
split into small particles (Zhang et al., 2015). In addition, a small amount of large-
cellophane, PP, and PE were observed most frequently in the Pearl River. size microplastics (4
These polymers are widely used in the packaging industry, which indicates
e5 mm) was observed only in the GUS and not in the PRE.
that urban pollution might be an important source of these microplastics.
Small particles can more easily be carried away by runoff, thus larger ones
Polypropylene and PE are the most frequently reported polymer types in
remained in the tributaries (Hurley and Nizzetto, 2018).
microplastics from coastal environment (Hidalgo-Ruz et al., 2012), which
Moreover, we found that most of the microplastics here were classified as
accounted for a relatively minor proportion here. A previous study, which was
film and granule. High proportions of fragment and film were also determined
focused on sewage sludge from wastewater treatment plants in China,
in water from Lake Hovsgol in Mongolia and Tamar Estuary in the UK (Free et
revealed that microplastics in the shape of films were mainly composed of
M. Yan et al. / Chemosphere 217 (2019) 879e886 885
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